2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
36 //// Local definitions
41 // Values modified by Joona Kiiski
42 const Value MidgameLimit = Value(15581);
43 const Value EndgameLimit = Value(3998);
45 // Polynomial material balance parameters
46 const Value RedundantQueenPenalty = Value(320);
47 const Value RedundantRookPenalty = Value(554);
49 const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
51 const int QuadraticCoefficientsSameColor[][6] = {
52 { 7, 7, 7, 7, 7, 7 }, { 39, 2, 7, 7, 7, 7 }, { 35, 271, -4, 7, 7, 7 },
53 { 7, 25, 4, 7, 7, 7 }, { -27, -2, 46, 100, 56, 7 }, { 58, 29, 83, 148, -3, -25 } };
55 const int QuadraticCoefficientsOppositeColor[][6] = {
56 { 41, 41, 41, 41, 41, 41 }, { 37, 41, 41, 41, 41, 41 }, { 10, 62, 41, 41, 41, 41 },
57 { 57, 64, 39, 41, 41, 41 }, { 50, 40, 23, -22, 41, 41 }, { 106, 101, 3, 151, 171, 41 } };
59 typedef EndgameEvaluationFunctionBase EF;
60 typedef EndgameScalingFunctionBase SF;
61 typedef map<Key, EF*> EFMap;
62 typedef map<Key, SF*> SFMap;
64 // Endgame evaluation and scaling functions accessed direcly and not through
65 // the function maps because correspond to more then one material hash key.
66 EvaluationFunction<KmmKm> EvaluateKmmKm[] = { EvaluationFunction<KmmKm>(WHITE), EvaluationFunction<KmmKm>(BLACK) };
67 EvaluationFunction<KXK> EvaluateKXK[] = { EvaluationFunction<KXK>(WHITE), EvaluationFunction<KXK>(BLACK) };
68 ScalingFunction<KBPsK> ScaleKBPsK[] = { ScalingFunction<KBPsK>(WHITE), ScalingFunction<KBPsK>(BLACK) };
69 ScalingFunction<KQKRPs> ScaleKQKRPs[] = { ScalingFunction<KQKRPs>(WHITE), ScalingFunction<KQKRPs>(BLACK) };
70 ScalingFunction<KPsK> ScaleKPsK[] = { ScalingFunction<KPsK>(WHITE), ScalingFunction<KPsK>(BLACK) };
71 ScalingFunction<KPKP> ScaleKPKP[] = { ScalingFunction<KPKP>(WHITE), ScalingFunction<KPKP>(BLACK) };
73 // Helper templates used to detect a given material distribution
74 template<Color Us> bool is_KXK(const Position& pos) {
75 const Color Them = (Us == WHITE ? BLACK : WHITE);
76 return pos.non_pawn_material(Them) == VALUE_ZERO
77 && pos.piece_count(Them, PAWN) == 0
78 && pos.non_pawn_material(Us) >= RookValueMidgame;
81 template<Color Us> bool is_KBPsK(const Position& pos) {
82 return pos.non_pawn_material(Us) == BishopValueMidgame
83 && pos.piece_count(Us, BISHOP) == 1
84 && pos.piece_count(Us, PAWN) >= 1;
87 template<Color Us> bool is_KQKRPs(const Position& pos) {
88 const Color Them = (Us == WHITE ? BLACK : WHITE);
89 return pos.piece_count(Us, PAWN) == 0
90 && pos.non_pawn_material(Us) == QueenValueMidgame
91 && pos.piece_count(Us, QUEEN) == 1
92 && pos.piece_count(Them, ROOK) == 1
93 && pos.piece_count(Them, PAWN) >= 1;
102 /// EndgameFunctions class stores endgame evaluation and scaling functions
103 /// in two std::map. Because STL library is not guaranteed to be thread
104 /// safe even for read access, the maps, although with identical content,
105 /// are replicated for each thread. This is faster then using locks.
107 class EndgameFunctions {
111 template<class T> T* get(Key key) const;
114 template<class T> void add(const string& keyCode);
116 static Key buildKey(const string& keyCode);
117 static const string swapColors(const string& keyCode);
119 // Here we store two maps, for evaluate and scaling functions...
120 pair<EFMap, SFMap> maps;
122 // ...and here is the accessing template function
123 template<typename T> const map<Key, T*>& get() const;
126 // Explicit specializations of a member function shall be declared in
127 // the namespace of which the class template is a member.
128 template<> const EFMap& EndgameFunctions::get<EF>() const { return maps.first; }
129 template<> const SFMap& EndgameFunctions::get<SF>() const { return maps.second; }
136 /// MaterialInfoTable c'tor and d'tor, called once by each thread
138 MaterialInfoTable::MaterialInfoTable() {
140 entries = new MaterialInfo[MaterialTableSize];
141 funcs = new EndgameFunctions();
143 if (!entries || !funcs)
145 cerr << "Failed to allocate " << MaterialTableSize * sizeof(MaterialInfo)
146 << " bytes for material hash table." << endl;
147 Application::exit_with_failure();
149 memset(entries, 0, MaterialTableSize * sizeof(MaterialInfo));
152 MaterialInfoTable::~MaterialInfoTable() {
159 /// MaterialInfoTable::game_phase() calculates the phase given the current
160 /// position. Because the phase is strictly a function of the material, it
161 /// is stored in MaterialInfo.
163 Phase MaterialInfoTable::game_phase(const Position& pos) {
165 Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
167 if (npm >= MidgameLimit)
168 return PHASE_MIDGAME;
170 if (npm <= EndgameLimit)
171 return PHASE_ENDGAME;
173 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
176 /// MaterialInfoTable::get_material_info() takes a position object as input,
177 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
178 /// If the material configuration is not already present in the table, it
179 /// is stored there, so we don't have to recompute everything when the
180 /// same material configuration occurs again.
182 MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
184 Key key = pos.get_material_key();
185 unsigned index = unsigned(key & (MaterialTableSize - 1));
186 MaterialInfo* mi = entries + index;
188 // If mi->key matches the position's material hash key, it means that we
189 // have analysed this material configuration before, and we can simply
190 // return the information we found the last time instead of recomputing it.
194 // Clear the MaterialInfo object, and set its key
195 memset(mi, 0, sizeof(MaterialInfo));
196 mi->factor[WHITE] = mi->factor[BLACK] = uint8_t(SCALE_FACTOR_NORMAL);
200 mi->gamePhase = MaterialInfoTable::game_phase(pos);
202 // Let's look if we have a specialized evaluation function for this
203 // particular material configuration. First we look for a fixed
204 // configuration one, then a generic one if previous search failed.
205 if ((mi->evaluationFunction = funcs->get<EF>(key)) != NULL)
208 if (is_KXK<WHITE>(pos) || is_KXK<BLACK>(pos))
210 mi->evaluationFunction = is_KXK<WHITE>(pos) ? &EvaluateKXK[WHITE] : &EvaluateKXK[BLACK];
214 if ( pos.pieces(PAWN) == EmptyBoardBB
215 && pos.pieces(ROOK) == EmptyBoardBB
216 && pos.pieces(QUEEN) == EmptyBoardBB)
218 // Minor piece endgame with at least one minor piece per side and
219 // no pawns. Note that the case KmmK is already handled by KXK.
220 assert((pos.pieces(KNIGHT, WHITE) | pos.pieces(BISHOP, WHITE)));
221 assert((pos.pieces(KNIGHT, BLACK) | pos.pieces(BISHOP, BLACK)));
223 if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
224 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
226 mi->evaluationFunction = &EvaluateKmmKm[WHITE];
231 // OK, we didn't find any special evaluation function for the current
232 // material configuration. Is there a suitable scaling function?
234 // We face problems when there are several conflicting applicable
235 // scaling functions and we need to decide which one to use.
238 if ((sf = funcs->get<SF>(key)) != NULL)
240 mi->scalingFunction[sf->color()] = sf;
244 // Generic scaling functions that refer to more then one material
245 // distribution. Should be probed after the specialized ones.
246 // Note that these ones don't return after setting the function.
247 if (is_KBPsK<WHITE>(pos))
248 mi->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
250 if (is_KBPsK<BLACK>(pos))
251 mi->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
253 if (is_KQKRPs<WHITE>(pos))
254 mi->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
256 else if (is_KQKRPs<BLACK>(pos))
257 mi->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
259 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == VALUE_ZERO)
261 if (pos.piece_count(BLACK, PAWN) == 0)
263 assert(pos.piece_count(WHITE, PAWN) >= 2);
264 mi->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
266 else if (pos.piece_count(WHITE, PAWN) == 0)
268 assert(pos.piece_count(BLACK, PAWN) >= 2);
269 mi->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
271 else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
273 // This is a special case because we set scaling functions
274 // for both colors instead of only one.
275 mi->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
276 mi->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
280 // Compute the space weight
281 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >=
282 2*QueenValueMidgame + 4*RookValueMidgame + 2*KnightValueMidgame)
284 int minorPieceCount = pos.piece_count(WHITE, KNIGHT)
285 + pos.piece_count(BLACK, KNIGHT)
286 + pos.piece_count(WHITE, BISHOP)
287 + pos.piece_count(BLACK, BISHOP);
289 mi->spaceWeight = minorPieceCount * minorPieceCount;
292 // Evaluate the material balance
293 const int pieceCount[2][6] = { { pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(WHITE, PAWN), pos.piece_count(WHITE, KNIGHT),
294 pos.piece_count(WHITE, BISHOP), pos.piece_count(WHITE, ROOK), pos.piece_count(WHITE, QUEEN) },
295 { pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
296 pos.piece_count(BLACK, BISHOP), pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
298 int sign, pt1, pt2, pc;
299 int v, vv, matValue = 0;
301 for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
303 // No pawns makes it difficult to win, even with a material advantage
304 if ( pos.piece_count(c, PAWN) == 0
305 && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
307 if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
308 || pos.non_pawn_material(c) < RookValueMidgame)
312 switch (pos.piece_count(c, BISHOP)) {
326 // Redundancy of major pieces, formula based on Kaufman's paper
327 // "The Evaluation of Material Imbalances in Chess"
328 // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
329 if (pieceCount[c][ROOK] >= 1)
330 matValue -= sign * ((pieceCount[c][ROOK] - 1) * RedundantRookPenalty + pieceCount[c][QUEEN] * RedundantQueenPenalty);
332 them = opposite_color(c);
335 // Second-degree polynomial material imbalance by Tord Romstad
337 // We use PIECE_TYPE_NONE as a place holder for the bishop pair "extended piece",
338 // this allow us to be more flexible in defining bishop pair bonuses.
339 for (pt1 = PIECE_TYPE_NONE; pt1 <= QUEEN; pt1++)
341 pc = pieceCount[c][pt1];
345 vv = LinearCoefficients[pt1];
347 for (pt2 = PIECE_TYPE_NONE; pt2 <= pt1; pt2++)
348 vv += pieceCount[c][pt2] * QuadraticCoefficientsSameColor[pt1][pt2]
349 + pieceCount[them][pt2] * QuadraticCoefficientsOppositeColor[pt1][pt2];
353 matValue += sign * v;
355 mi->value = int16_t(matValue / 16);
360 /// EndgameFunctions member definitions.
362 EndgameFunctions::EndgameFunctions() {
364 add<EvaluationFunction<KNNK> >("KNNK");
365 add<EvaluationFunction<KPK> >("KPK");
366 add<EvaluationFunction<KBNK> >("KBNK");
367 add<EvaluationFunction<KRKP> >("KRKP");
368 add<EvaluationFunction<KRKB> >("KRKB");
369 add<EvaluationFunction<KRKN> >("KRKN");
370 add<EvaluationFunction<KQKR> >("KQKR");
371 add<EvaluationFunction<KBBKN> >("KBBKN");
373 add<ScalingFunction<KNPK> >("KNPK");
374 add<ScalingFunction<KRPKR> >("KRPKR");
375 add<ScalingFunction<KBPKB> >("KBPKB");
376 add<ScalingFunction<KBPPKB> >("KBPPKB");
377 add<ScalingFunction<KBPKN> >("KBPKN");
378 add<ScalingFunction<KRPPKRP> >("KRPPKRP");
381 EndgameFunctions::~EndgameFunctions() {
383 for (EFMap::const_iterator it = maps.first.begin(); it != maps.first.end(); ++it)
386 for (SFMap::const_iterator it = maps.second.begin(); it != maps.second.end(); ++it)
390 Key EndgameFunctions::buildKey(const string& keyCode) {
392 assert(keyCode.length() > 0 && keyCode[0] == 'K');
393 assert(keyCode.length() < 8);
398 // Build up a fen string with the given pieces, note that
399 // the fen string could be of an illegal position.
400 for (size_t i = 0; i < keyCode.length(); i++)
402 if (keyCode[i] == 'K')
405 s << char(upcase ? toupper(keyCode[i]) : tolower(keyCode[i]));
407 s << 8 - keyCode.length() << "/8/8/8/8/8/8/8 w - -";
408 return Position(s.str(), 0).get_material_key();
411 const string EndgameFunctions::swapColors(const string& keyCode) {
413 // Build corresponding key for the opposite color: "KBPKN" -> "KNKBP"
414 size_t idx = keyCode.find("K", 1);
415 return keyCode.substr(idx) + keyCode.substr(0, idx);
419 void EndgameFunctions::add(const string& keyCode) {
421 typedef typename T::Base F;
422 typedef map<Key, F*> M;
424 const_cast<M&>(get<F>()).insert(pair<Key, F*>(buildKey(keyCode), new T(WHITE)));
425 const_cast<M&>(get<F>()).insert(pair<Key, F*>(buildKey(swapColors(keyCode)), new T(BLACK)));
429 T* EndgameFunctions::get(Key key) const {
431 typename map<Key, T*>::const_iterator it = get<T>().find(key);
432 return it != get<T>().end() ? it->second : NULL;